1. Field of the Invention
The present invention relates generally to a multiband mobile communication terminal, and in particular, to an automatic antenna device and method for automatically controlling an extended length of a whip antenna according to frequency bands.
2. Description of the Related Art
With the rapid development of mobile communication technology, various communication services are presently provided that use different communication systems and standards. At present, these services are not compatible with one another. Therefore, it is necessary to allow an existing mobile communication system to work with another mobile communication system. For example, have an existing CDMA (Code Division Multiple Access) terminal with a PCS (Personal Communication System) terminal; an existing AMPS (Advanced Mobile Phone Service) terminal with an US (United States) PCS terminal; and an existing GSM (Group Special Mobile) terminal with a DECT (Digital European Cordless Telephone) terminal or a DCS-1800 (Digital Communication System-1800) terminal which is a GSM terminal applied to a 1,800 MHz band. In addition, it is also necessary to allow more than three different communication systems to work with one another. A mobile communication terminal which can operate simultaneously with two or more communication systems is called a dualband or multiband mobile communication terminal. Conventionally, the multiband mobile communication terminal has an antenna device comprised of multiple antennas according to the frequency bands received. This results in an increase in the size and the cost of the terminal. Alternatively, the conventional multiband mobile communication terminal having a single antenna includes an antenna matching circuit to support the multiple frequency bands. This results in an increase in complexity.